I am writing a query to find employees who earn greater than the average salary within their department. I need to display the employee ID, salary, department id, and average salary of that department.
I have a query that just almost works but it keeps giving me "ORA-00904: "AVG_SAL": invalid identifier" errors. Am I doing this correctly. Why am i getting this invalid identifier error?
SELECT employee_id, salary, department_id,
(SELECT ROUND(AVG(salary),2)
FROM employees e_inner
WHERE e_inner.department_id = e.department_id) AS avg_sal
FROM employees e
WHERE salary > avg_sal
ORDER BY avg_sal DESC
I don't believe you can refer to a column alias (avg_sal in this case) in a WHERE clause.
You'll need to repeat that inner query, i.e.:
SELECT employee_id, salary, department_id,
(SELECT ROUND(AVG(salary),2)
FROM employees e_inner
WHERE e_inner.department_id = e.department_id) AS avg_sal
FROM employees e
WHERE salary >
(SELECT ROUND(AVG(salary),2)
FROM employees e_inner
WHERE e_inner.department_id = e.department_id)
ORDER BY avg_sal DESC
Not great, with those two inner queries, but that's the most-straightforward way to correct the error.
Update: Haven't tested this, but try the following:
SELECT e.employee_id, e.salary, e.department_id, b.avg_sal
FROM employees e
INNER JOIN
(SELECT department_id, ROUND(AVG(salary),2) AS avg_sal
FROM employees
GROUP BY department_id) e_avg ON e.department_id = e_avg.department_id AND e.salary > e_avg.avg_sal
ORDER BY e_avg.avg_sal DESC